How would you like to take your Mac with you in your pocket? Until Apple builds a Macbook Mini, the most portable, powerful Mac you'll ever have is the one you set up yourself. All you need is a USB hard drive and a little time, and when you're done, you'll have a perfect copy of your Mac in your pocket that you can use to boot any other Mac you find, clone a loaner computer in case your primary breaks down, and keep a headless backup of your Mac for troubleshooting wherever you go.

OS X makes it super-easy to clone your entire hard drive to a USB device, and then boot from the USB device instead of from the hard drive in your system and work like normal. That means it's really easy to take your Mac with you on an external hard drive and get to work without missing a beat.

Why You Need a Portable Mac In Your Pocket

Keeping a portable Mac in your pocket can ensure you're productive from anywhere and can make you a Mac troubleshooting master. Here's what we mean:

Troubleshooting: If you're the type who likes to tinker with your system, having a bootable Mac-on-a-drive makes it possible for you to troubleshoot system issues anytime, anywhere. Load up your drive with testing tools and repair utilities, and you're never without a way to fix—or restore—an ailing Mac.

Portability: Keeping a bootable Mac on a drive means that anywhere you have access to Mac hardware is a place you can work. If you don't have a Macbook Pro or Air, or just don't want to lug it with you, your bootable hard drive can give you all the tools you need to be productive anywhere you go.

Loaner Systems: If you have to send your system away for repairs, being without it for days at a time doesn't mean you can't get your work done. Even if you don't want to just boot to your hard drive, you can always use the drive to image a loaner system, get your work done, re-image your Mac when it comes back, and wipe the loaner.

Backups: The most obvious benefit is that you'll always have a drive to image your Mac's current system to, whether you use the drive as bootable storage for dated images, or you re-image the drive periodically so you can essentially boot to your Mac whenever you need to.

If these sound good to you, you're in luck—getting your own pocket-sized bootable Mac takes a matter of minutes.

What You'll Need

Ready to get started? Here's what you'll need:

A Mac running any version of OS X (10.4 or higher, ideally.)

A portable external hard drive that's at least the same size (preferably larger) than your Mac's boot drive. This 1TB Western Digital USB 3.0 drive will set you back under $100, offers tons of space, and is small enough to go anywhere.

Step One: Clone Your Current Mac

Once you've assembled all of your tools, the first thing you'll want to do is format your external hard drive and clone your Mac to it. Install Carbon Copy Cloner, and connect your external USB drive. From there, here's what you'll need to do.

Format Your External Drive: Your new external drive probably has a pre-bundled crap on it you don't want. Plus, we need to format the drive so your Mac can boot from it.

Open Disk Utility (Applications Folder > Utilities Folder), and select your new drive from the list on the left.

Select "Partition" from the tabs on the right. If you'd like to partition the drive—to have a bootable volume and a data volume on the same hard drive, for example—now is the time to do it. Make sure your partitions have names, and next to "Format" on the right, you have "Mac OS Extended (Journaled) selected.

Next, select the partition you want to be bootable (or the only one, if you're sticking to one partition), and click "Options" at the bottom of the screen.

Select "GUID Partition Table" from the three options here. This will allow you to boot an Intel-based Mac to the external hard drive. Click Ok. You'll be prompted to confirm your choice. Click Ok again.

Clone Your Mac: After Disk Utility partitions and formats your external drive, it's time to clone your system over to it.

Close Disk Utility and fire up Carbon Copy Cloner.

The first window you'll see will ask you to select a source on the left and a destination on the right. Choose your Mac's internal drive as the source, and your external hard drive as the destination. From here, you can deselect any items you don't want to clone, but we'd suggest keeping everything. After all, you want your bootable drive to be a perfect copy of your Mac.

Click "Clone" to kick the process off.

Grab A Drink: Depending on the size of your Mac's drive and how much data you have on it, this process can take a while - over an hour if you have a lot of data to copy. This might be something you want to let run overnight, if you're moving from large drive to large drive.

Step Two: Boot to Your Portable Mac

Once Carbon Copy Cloner is done, it'll pop up an alert to let you know the cloning process is finished. Put your drink down: it's time to test the drive and make sure it works. Open up System Preferences, and select "Startup Disk." You should see your newly cloned hard drive in the list. Select it, and click "Restart." Alternatively, press and hold the Option key the next time you start up your Mac with the drive attached—you'll get dropped into the startup manager, and you can select your newly cloned drive from there.

Once your system is up and running, it should look, behave, and operate exactly like your Mac—you should just have much more free space (or an extra partition, if you created a data volume.) Check and make sure your applications work (some apps with strict licensing may need to be re-registered or have their license keys re-entered).

Once you've verified that everything's working, you're ready to go: Pop that drive in your pocket and you have the power to boot any Mac you find, any time, anywhere, and land on your desktop, with your wallpaper and your apps and files. Just follow the same steps from any Mac:

Plug your OS X boot drive into any Mac

Open System Preferences and select "Startup Disk."

Select your cloned hard drive from the list and click "Restart."

Step Three: Tweak Your Portable Mac

Now that you have your portable Mac ready for use, it's time to customize the build. If you wanted your pocket Mac for system troubleshooting, now's the time to install some system utilities on it that you wouldn't normally be able to run against your Mac's internal hard drive if you were booted up to it directly. Here are a few suggestions:

Cocktail is a great system maintenance and optimization tool to clean out temporary files and caches, defrag your startup disk, check your Mac's drive health, and more.

Diskwarrior repairs ailing hard drives, and can recover data from drives that Disk Utility has trouble verifying or repairing. It's pricey at $99, but if your drive is dying and you need something from it, it may be worth it.

Tech Tool Pro is controversial, mostly because it too is $99 and Micromat will charge you for every update, upgrade, or feature improvement, but it has one of the most comprehensive hardware testing suites I've seen. It's an old tool and has been around for a long time—I wouldn't use it to try and fix problems so much as firmly prove whether the issues you have are hardware-related or software-based.

Disk Utility and Carbon Copy Cloner themselves work better when you're booted to a drive other than the one you're trying to verify, repair, or back up, so keep them installed as well. The beautiful thing about using your drive for troubleshooting is that you can fix problems with not just your main Mac, but anyone else's Mac. You can diagnose hardware problems that Apple Store Geniuses can't figure out, and even reinstall OS X entirely—all from your pocket.

If you're optimizing your portable Mac for productivity, you're already set—it's a perfect copy of your main Mac. If you're building your USB drive so you can install Mac OS on other systems, follow our guide to building a Lion install USB drive using a partition on your external drive—but a better method would be to take an image of a perfectly set up Mac—complete with all the apps and settings you'd want so you can get right to work—and store that on your external drive. Then, instead of just installing OS X, you can image any new Mac with the OS, applications, and settings you want. In fact, you can use the drive to take regular, dated images of your Mac's internal drive, just to keep them as whole-system backups you can restore from at any time.

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Be Aware of Your Limitations

This method works well with Macs running OS X 10.4 "Tiger" forward. Just be careful that you're booting a Mac with the same operating system on it. You may run into issues trying to boot an older OS to a Mac that shipped with a newer one on it (trying to boot Leopard to a Mac that shipped with Lion, for example) but you shouldn't have a problem as long as your portable Mac is up to date and running the most recent version of the OS. Keep that in mind if you run into issues trying to boot a Mac with your drive and it's not recognizing your USB drive as a startup device.

Even if you don't spend money on expensive troubleshooting tools, or opt for an external hard drive that doesn't necessarily fit in your pocket, cloning your current Mac to an external hard drive has a world of benefits—the least of which is giving you a version of your Mac that you can use if your boot drive is all mucked up. Do you have any other troubleshooting tools you'd suggest for that external drive? Have you done this before and have some more tips to share? Let us know in the discussions below.